The present invention relates generally to analytical test devices and, more particularly, to a rotatable test element and method for detecting an analyte with the aid of the test element.
In principle the systems for analysing liquid sample materials or sample materials which can be converted into a liquid form can be divided into two classes. On the one hand, there are analytical systems which operate exclusively with so-called wet reagents and, on the other hand, there are systems which use so-called dry reagents. In particular in medical diagnostics and also in environmental and process analytics the former systems are primarily used in permanently equipped laboratories whereas the latter systems are used mainly for “on-site” analyses.
Analytical systems using dry reagents are offered in the field of medical diagnostics especially in the form of so-called test carriers, e.g., test strips. Prominent examples of this are test strips for determining the blood sugar value or test strips for urine analyses. Such test carriers usually integrate several functions (e.g., the storage of reagents in a dried form or, although more rare, in solution; the separation of undesired sample components in particular red blood corpuscles from whole blood; in the case of immunoassays the so-called bound free separation; the metering of sample volumes; the transport of sample liquid from outside a device into the interior of a device; the control of the chronological sequence of individual reaction steps, etc.). In this connection the function of sample transport is often effected by means of absorbent materials (e.g., papers or fleeces), by means of capillary channels or by using external driving forces (such as, e.g., pressure, suction) or by means of centrifugal force. Disk-shaped test carriers, so-called lab-disks or optical bio-disks pursue the idea of controlled sample transport by means of centrifugal force. Such disk-shaped, compact disk-like test carriers allow a miniaturization by utilizing microfluidic structures and at the same time enable processes to be carried out in parallel by the repeated application of identical structures for the parallel processing of similar analyses from one sample or of identical analyses from different samples. Especially in the field of optical bio-disks it is possible to integrate optically stored digital data for identifying the test carrier or for the control of analytical systems on the optical bio-disks.
In addition to miniaturization and parallelization of analyses and integration of digital data on optical disks, bio-disks generally have the advantage that they can be manufactured by established manufacturing processes and can be measured by means of an established evaluation technology. In the case of the chemical and biochemical components of such optical bio-disks it is usually possible to make use of known chemical and biochemical components. A disadvantage of the optical lab-disks or bio-disks that are based purely on centrifugal and capillary forces is that it is difficult to immobilize reagents and the accuracy of the detection suffers. Especially in the case of detection systems which are based on specific binding reactions, such as e.g., immunoassays, there is an absence of the volume component compared to conventional test strip systems especially in the so-called bound-free separation.
For this reason attempts have recently been made especially in the field of immunoassays to establish hybrids of conventional test strips and bio-disks. This results in bio-disks with channels and channel-like structures for liquid transport, on the one hand, and voluminous absorbent materials in these structures (at least partially), on the other hand.
A disadvantage of the concepts of the prior art is that a specific control of the reaction and dwelling times of the sample liquid after uptake of the reagents and after they have flowed into the porous, absorbent matrix is not possible especially for specific binding assays such as, e.g., immunoassays.